I've noticed that there are very interesting photo talks in the Wildlife section, and some tidbits in other threads, but there doesn't seem to be a dedicated thread for all things photography. I understand it's not mandatory on such a forum, but since we have talentuous contributors, whether in photography or photoplasty, I just wanted to get past their modesty, show my own ignorance of the subject at large, and open this new thread.

--------------"Hail is made out of water? Are you really that stupid?" Joe G

"I have a better suggestion, Kris. How about a game of hide and go fuck yourself instead." Louis

"The reason people use a crucifix against vampires is that vampires are allergic to bullshit" Richard Pryor

Well, my setup is a Canon EOS T2i matched to a Tamron DiII 18-270mm travel lens. I'd like to get something with a little faster continuous shooting (the T2i is only 3.7 fps), but I'm not ready to shell out the greenbacks right now.

This is probably my favorite picture. I realize it is more than a little derivative, but I like it anyways.

ETA: Lake Quanah Parker in the Wichita Mountains Wildlife Refuge.

Edited by carlsonjok on April 18 2012,08:04

--------------It's natural to be curious about our world, but the scientific method is just one theory about how to best understand it. We live in a democracy, which means we should treat every theory equally. - Steven Colbert, I Am America (and So Can You!)

Well, my setup is a Canon EOS T2i matched to a Tamron DiII 18-270mm travel lens. I'd like to get something with a little faster continuous shooting (the T2i is only 3.7 fps), but I'm not ready to shell out the greenbacks right now.

This is probably my favorite picture. I realize it is more than a little derivative, but I like it anyways.

Well, when a man and woman love each other very much and want to make a baby.........

--------------It's natural to be curious about our world, but the scientific method is just one theory about how to best understand it. We live in a democracy, which means we should treat every theory equally. - Steven Colbert, I Am America (and So Can You!)

f-stops are a measure of light-gathering or light transmission capability.

Start with a pinhole. A small hole will serve to produce an image. The closer it is to the image plane, the brighter the resulting image is. So for a fixed aperture, or size of hole, the distance from image plane to the pinhole can change the amount of light arriving at the image plane. For a pinhole, the distance from the image plane can be treated as the focal length. A smaller pinhole that is closer to the image plane and a larger pinhole that is further from the image plane will produce the same amount of light impinging on the image plane. You can, in fact, derive a formula for this equivalent light-passing capability:

f-stop = {focal length} / {diameter of aperture}

Small f-stop numbers indicate aperture diameters closer to the focal length. Larger f-stop numbers mean the aperture diameter is small relative to the focal length.

Now, pinholes have to have a high f-stop in order for the images produced to look anywhere near sharp. When we start thinking about lenses, these can be considered ways to make our pinholes larger without losing so much sharpness. The lens elements focus light paths diverging from a subject that touch all across their surface to (just about) one point. (If the lens is well-adjusted, etc.)

An f-stop is easily calculated and works for just about anything you put in front of a piece of film or a sensor. Handheld light meters for photography simply present shutter speed and aperture combinations to tell the measured light level, which is pretty impressive given how many different lenses have been produced over the history of man's use of optics.

But f-stops are not the whole story. Passing light through a complex lens with many elements will tend to lose a small amount of light to reflection at each surface encountered on the way in. Modern lenses have coatings on the surfaces to reduce this light loss. The cinematic folks tend to use lenses that have T-stop ratings. These are on the same scale as f-stops, but take into account the particular light loss that each lens has.

There are tradeoffs. Getting lower f-stop numbers and thus greater light-gathering capability requires larger pieces of glass and more esoteric means of correcting optical errors that refraction introduces into images. That means that "faster" glass is more expensive to make. A common "fast" f-stop is f/2.8, or a light-gathering element with an effective diameter just a bit larger than one-third the focal length. Once you get past f/5.6, certain features like autofocus tend not to work. Those need a certain amount of light to do their work. Lou's new lens is an f/1.2, an exceptionally fast lens. It will permit almost three stops or eight times as much light through it wide-open as will an f/2.8 lens.

For folks using auto-focus and auto-exposure, the transmission factor of the glass is irrelevant, unless one brand is crappy compared to another.

Movie makers need to work like Ansel Adams and control the luminosity of ever element in the frame. Or at least know how it's going to look.

That's why actors sit around for hours sometimes, waiting for the light to get right.

That's a bit too glib. Unless you are using a Nikon D4, your 500mm f/8 mirror reflex lens would not autofocus even if it had autofocus capability. Autofocus modules stop working somewhere around f/5.6 to f/6.3. The D4 applies some of its high ISO capability to its autofocus module, which will accommodate lenses out to f/8.

This more commonly gets encountered when using teleconverters. A lens that will autofocus fine on its own will often fail to do so when you add a 2x teleconverter and essentially add 2 to its maximum f-stop. [ETA: That's unclear... you have to treat the lens as being two more f-stops slower, so an f/4 lens with a 2x teleconverter would be equivalent to an f/8 lens, while an f/5.6 lens would be equivalent to an f/11 lens.]

Autoexposure shouldn't have that working limit, but you do have to account for other transmission losses if you want to use handheld light meters that aren't tied into the optical system at issue and are using sensors or emulsions with limited dynamic range. Losing a half-stop or more of accuracy simply is not acceptable under critical use conditions. Calibration is essential then, and that is what Ansel Adams was famous for in his advocacy of the Zone System.

Well, my setup is a Canon EOS T2i matched to a Tamron DiII 18-270mm travel lens. I'd like to get something with a little faster continuous shooting (the T2i is only 3.7 fps), but I'm not ready to shell out the greenbacks right now.

This is probably my favorite picture. I realize it is more than a little derivative, but I like it anyways.

ETA: Lake Quanah Parker in the Wichita Mountains Wildlife Refuge.

It's a sweet shot, Carlson. Did you slap any HDR on that, or is that a single shot?

I've been playing a little bit with HDR (Photomatrix Pro on some throw-away landscape shots), but I haven't yet really gotten the hang of it.

I did go out and shoot some dead cypress trees for a PhD candidate in my lab for a poster he did regarding his research on salt-water intrusion, and they came out great on his poster (and I got a photo credit, yay!).

This is an HDR composite and a mosaic of about 9 shots total from that excursion.

--------------Lou FCD is still in school, so we should only count him as a baby biologist. -carlsonjok -deprecatedI think I might love you. Don't tell Deadman -Wolfhound

I was addressing autoexposure, which works regardless of whether the lens aperture is calibrated correctly. With a digital camera you can have it do auto bracketing, and if you shoot RAW, you generally have enough latitude to make a good image, except in the most contrasty situations.

And if you are in that situation, HDR is the way to go.

Of course moving subjects and fleeting opportunities can make a hash of this, in which case you're stuck with autoexposure.

--------------Any version of ID consistent with all the evidence is indistinguishable from evolution.

I'm still trying to convince Ali to sign up here and join the discussion. She loves photograpy and has a Canon 1000something with two gunbarrel-looking stuff to attach to it and seems to know about them (although I believe she's just pretending just to look smug). She's a frequent onlooker.

Lou, this thread is dedicated to you because you had a happy dance, and other than Katrine (and Louis), I don't know many that do.

Wes, I would love some schematics :)

--------------"Hail is made out of water? Are you really that stupid?" Joe G

"I have a better suggestion, Kris. How about a game of hide and go fuck yourself instead." Louis

"The reason people use a crucifix against vampires is that vampires are allergic to bullshit" Richard Pryor

It's a sweet shot, Carlson. Did you slap any HDR on that, or is that a single shot?

That was a single shot. Straight out of the camera it didn't have that much contrast. Most of the effect was from post-processing.

Original:

I adjusted the white and black point in Photoshop to add some contrast.

I then put a black and white layer on top of that.

Then cranked down the blues and reds, and bumped up the yellows to get the final product.

It was a bit of a cheat. The ominous feeling of the final product really wasn't there at the start.

--------------It's natural to be curious about our world, but the scientific method is just one theory about how to best understand it. We live in a democracy, which means we should treat every theory equally. - Steven Colbert, I Am America (and So Can You!)

I was addressing autoexposure, which works regardless of whether the lens aperture is calibrated correctly. With a digital camera you can have it do auto bracketing, and if you shoot RAW, you generally have enough latitude to make a good image, except in the most contrasty situations.

And if you are in that situation, HDR is the way to go.

Of course moving subjects and fleeting opportunities can make a hash of this, in which case you're stuck with autoexposure.

I'm not sure what you think there is an argument about.

Let's look at what I responded to:

Quote

Can someone explain what that f.. stuff means?

Care to tell me how "Pay no attention to that, autoexposure will take care of it" counts as an explanation, or even a contribution to an explanation?

I wasn't trying to agree or disagree. Just adding what I thought was a useful comment.

I've been around cameras for a few years. I still have a working Nikon F bought in 1965. I was a darkroom technician for four college yearbooks and made the final prints for three. I never used a camera with any automatic features for the first ten years I was in the hobby.

I sold darkroom equipment at Altman Camera in Chicago in 1970 and 71. At the time it was the largest camera store in the world.

Your explanation is fine. I learned something from the discussion of t-stops. I just thought it left the impression that the effective f-stop is something to be concerned about, and I doubt that it is.

--------------Any version of ID consistent with all the evidence is indistinguishable from evolution.

I DO have a question on digital cameras, though. I came across a Bass Rumoure that DSLRs have serious problems with dust on the CCD. In particular, the electrostatic charge never goes away, and is not fixable.

I'm thinking of going to either a Canon G12 or Nikon equivalent, because you never open the camera body.

I'll take the liberty of pasting here a PM I sent to Lou quite a while ago about astronomic photography with a numeric camera.

Any and all corrections are welcome:

Quote

All you need is your digicam, a stable stand, Photoshop, and a clear night sky.

You will have to set the apperture time of your cam to something akin to a normal low-light shooting (sadly I don't have the exact ms timing, but a few tests should let you figure it out). If the exposure time is too long, you'll get weird artefacts due to the Earth rotation, which the stand doesn't compensate.

Choose a patch of sky you'd like to imortalise, and start shooting. A remote would be better than actually pushing the button every time. That way you are sure your cam will be aligned 100% of the time.

Take as many pics as you want (usually 10 is enough).

Now, open these 10 (or more) pics in Photoshop (or any other software that works with layer). That's the tricky part. The bottom layer (ie. first pic) will be 100% opacity. all other pics will be added on a new layer, with oppacity decreasing by 10% for each new layer. So if you took 20 pics, it will decrease by 5%, but you should know that, Mr PhD

Take any single star or body from the bottom-layer pic, and use it to align all the pics, thus compensating Earth's rotation.

You should come up with amazing images. My favorite, when I used to work on this, was the Milky Way, but Andromeda gives great results as well.

Everything is in the setting of your exposure time, so a few trials and errors are nescessary.

Hope this help, and if it does, please share your pics

--------------"Hail is made out of water? Are you really that stupid?" Joe G

"I have a better suggestion, Kris. How about a game of hide and go fuck yourself instead." Louis

"The reason people use a crucifix against vampires is that vampires are allergic to bullshit" Richard Pryor

I wasn't trying to agree or disagree. Just adding what I thought was a useful comment.

I've been around cameras for a few years. I still have a working Nikon F bought in 1965. I was a darkroom technician for four college yearbooks and made the final prints for three. I never used a camera with any automatic features for the first ten years I was in the hobby.

I sold darkroom equipment at Altman Camera in Chicago in 1970 and 71. At the time it was the largest camera store in the world.

Your explanation is fine. I learned something from the discussion of t-stops. I just thought it left the impression that the effective f-stop is something to be concerned about, and I doubt that it is.

Since the whole point of f-stops is supposed to be a metric of light transmission that is the same across disparate lenses, the explanation would be incomplete without discussion of how the simple f-stop metric isn't sufficient for that objective. That's still true whether current TTL metering makes deep knowledge of light transmission in optics moot for a segment of photographers.

I gave my last Nikon F to a friend, but I still have an F2 and a Beseler 45MX. I have yearbook photography, photojournalism, studio photography, public relations photography, and event photography in my work background, plus coursework in fine arts photography from U. Florida.

Since modern cameras measure exposure based on the light coming out of the ass end of the lens into the camera box, the exposure is based on the T-stop, not the F-stop, so stop your arguing, please. Yes, if you're using an external meter and if your lens' T-stop differs from the F-stop by an easily measureable amount and if you're shooting something like Velvia with 5-stop latitude you'll want to take this into consideration. Shooting digital RAW with the 14 stop latitude typical of modern DSLRs (at least my canon ones) ... not so much.

One problem the movie industry faces when shooting film is that prints distributed to theaters are literally contact prints of the negative the movie's shot on. Contact printing and bazillions of frames means there's no cost effective way to fix exposure errors, even minor ones, after the movie's shot.

The ability to manipulate the image in the darkroom while printing makes things flexible enough that still shooters have always been able to use F-stops. Adams may've talked about T-stops in The Zone System, I don't remember, but if he did, the whole exposure/film developer selection+time/development/paper selection/manipulaton during printing/paper developer selection+time dwarfed it like godzilla stomping bambi.

It is my impression that most major movies not are edited and corrected digitally.

I use the word corrected rather loosely, since the usual correction is to desaturate some portion of the spectrum for atmosphere. The most blatant example was O Brother Where Art Thou, which dropped out nearly all green.

I believe Spielberg liked to handle film, but since movies have to be released digitally anyway, I suspect they are edited digitally, with some final prints going back to film.

That's my suspicion. I'd be interested in knowing if it's true.

--------------Any version of ID consistent with all the evidence is indistinguishable from evolution.

Before I call out individual attributes, there's one thing I should mention: this lens is not f/4. Let me correct that: this lens is not t/4. (A t-stop is the actual transmitted light, an f-stop is the theoretical light transmission.) Actual performance is somewhere around t/5. This is somewhat normal for a zoom lens with complex optics (each air/glass surface is less than perfect in transmitting light), but it's going to be a real issue for many users of this lens. This is one of the reasons why teleconverters aren't a great choice on this lens. Even with a TC-14E the lens is approaching t/8, which is outside Nikon's AF specs.

You may not care about differences between nominal and actual light transmission. A lot of hobbyists with autoexposure equipment may not care. Other people do. That would include people who want to expose according to incident light rather than reflected light measures, or who want to choose a lens with the absolute best performance under difficult low-light conditions (something that isn't changed whether you use TTL metering or not). I'm assuming that it would also include people who want to understand the physics behind the equipment. I think my hackles got raised with the "irrelevant" phrasing in your original comment and the fact that you did at that point include autofocus in your response, and that was plainly incorrect.

Dhogaza, nobody here has at any time disputed the ability of TTL metering systems to adjust for individual light transmission differences. I'm going to have to disagree with a claim of yours. Using a film like Kodak Technical Pan developed for continuous tone (POTA, 15 minutes at 68 degrees F, no push, no pull, no nothing) that has essentially no shoulder in the highlights makes a transmission difference like the one in the lens mentioned above highly relevant and not something that would be swamped by other parts of the process. If you are using TTL autoexposure, that will (mostly) work out, but if you aren't, it will make an actual difference in your results if it isn't accounted for. I feel like I've fallen through the rabbit hole to a place where people who I know to value knowledge in other circumstances are suddenly arguing for the primacy of ignorance in this one.

Well we could always convert this into an argument about gnu atheism, but seriously, my comment had a very limited scope. I had no idea I was disagreeing with anything you said.

If you are reviewing lenses on the basis of transmission, you would be lenses of the same type, as in different brands and models.

Incident light metering is rather specialized. It's used in studios and in movie making, but I think anyone going to that kind of trouble would calibrate a system with actual test shots.

Back when shutters were mechanical and involved a moving slit of varying width, it was widely recognized that effective shutter speed didn't necessarily match nominal speed.

And if you developed your own film you noticed differences between brands and types of developer. I read, for example, that National Geographic had all of their film processed in one plant, and did not allow it to be done as the first batch of the day. They wanted assurance that the chemistry was right.

For 99.9 percent of people using digital cameras, these issues are irrelevant, even if interesting. I would bet not many people shooting RAW images would notice half an f-stop difference in exposure. In fact people routinely adjust the levels in their photos to make them "pop."

This can easily truncate several f-stops of shadow and highlight detail.

--------------Any version of ID consistent with all the evidence is indistinguishable from evolution.